Bond pads provide points of external electrical connection/probing for a semiconductor die. Hard and chemically stable electroless-plated bond pads such as NiP pads in combination with 4N (99.99% pure) Au bondwires have been used for probing and bonding over active areas of a semiconductor die. However, the electroless plating process used to form such a hard bond pad is complex and expensive. Additionally, electroless-plated bond pads are prone to copper voids in the last metallization layer of the semiconductor die. As such, direct routing in the uppermost metallization layer is typically forbidden by design rule. Otherwise, the weak interface at the side of an electroless-plated bond pad allows copper migration to the surface of the bond pad which can lead to undesirable intermetallic phase growth.
AlCu bond pads have been used for automotive technologies. However, AlCu bond pads are highly prone to barrier cracks and thus have low robustness. Cracks caused by probing can be a significant reliability risk, depending on the type of product. For these products, additional probe pads are typically provided to accommodate wafer probing, which increases die size and therefore cost per die.
Hence, there is a need for a robust bond pad that can be produced in a lost-cost manner.